At the Waterworks is the first book in the original book series, and the début of the franchise as a whole.
"Ms. Frizzle drives the Magic School Bus into a cloud where the children shrink to the size of water droplets and follow the course of water through the city's waterworks system."
The kids are unhappy and unlucky to know that they got Ms. Frizzle as their teacher, whom they call "the strangest teacher in school". They hate her because of the assignments she gives them, and the fact that they have to read five books a week. Ms. Frizzle tells the kids that they have a field trip to the waterworks the following day, and they have to get ready for it by providing ten interesting facts about water.
The kids head outside to the Magic School Bus, which, to their surprise, Ms. Frizzle is driving. As the students ride along, they enter a tunnel and find themselves in scuba gear. The Bus soon rises into the air and is parked on a cloud. Ms. Frizzle orders the students out of the Bus, threatening them with extra homework if they don't exit.
The kids and Ms. Frizzle shrink and find themselves inside their own raindrops as they rain into a river and get washed downstream. They travel through the water supply system into the town's water mains. Eventually, they get splashed out of the sink in the girls' bathroom at school, where they get back to normal size.
In class, Arnold draws a picture of a kid in a raindrop, prompting Ms. Frizzle to ask Arnold where he got those crazy ideas. Later, they paint a mural of the waterworks.
At lunch, Amanda Jane notices the Bus at the parking lot. She wonders why it's still at the school even though it was parked at a cloud.
- Regardless on this being the very first book of the series, this is also the first book that the Bus hasn't transformed into anything. The second time the Bus doesn't transform was in the third book, Inside The Human Body.
- On the original cover, the word "Waterworks" is colored blue and appears in the Magic School Bus logo font.
- On the 2004, 2006, and 2016 covers, the title of the book (excluding the 1997 TMSB logo) is used in the And the Electric Field Trip title font. Joanna Cole and Bruce Degen's credits appear on top of the MSB logo like in that book, without indicating which one wrote or illustrated it.
- The Bus's overhead sign has a picture of four water droplets on it on the cover, regardless of which edition of the book one is reading.
- On 21st-century publications, the 1997-2021 The Magic School Bus logo has white outlining on one cover, purple on another cover, and green on another cover.